This invention relates to ventilators, more particularly but not exclusively for use in rooms with sealed windows and/or double glazing where it is desirable to provide for ventilation without having to open the window. This type of ventilation is now often referred to as "secondary ventilation" and has in recent years been achieved by the insertion into a slot cut or formed in the surrounds of windows and the like of a slot ventilator. The inner end of the slot may be left open but is usually provided with a manually operable closure or a grill while on the outer side there is often a canopy extending outwardly and downwardly from the top of the slot and providing a downwardly facing opening which may incorporate an insect screen, the canopy thus shielding the slot from the ingress of rain and also dust and dirt.
It has been found that if the closure, when provided, is left open during windy conditions a draught blows through the ventilator. The present invention relates to improvements in such ventilation means and in particular has as an object the avoidance of such draughts.